U.S. patent application number 10/521973 was filed with the patent office on 2006-11-23 for phosphonium and imidazolium salts and methods of their preparation.
Invention is credited to Douglas Baumann, John H. Hillhouse, Allan J. Robertson, Yuehui Zhou.
Application Number | 20060264645 10/521973 |
Document ID | / |
Family ID | 31722360 |
Filed Date | 2006-11-23 |
United States Patent
Application |
20060264645 |
Kind Code |
A1 |
Zhou; Yuehui ; et
al. |
November 23, 2006 |
Phosphonium and imidazolium salts and methods of their
preparation
Abstract
Novel phosphonium and imidazolium salts and methods for
preparing them are disclosed. The novel phosphonium and imidazolium
compounds are useful as polar solvents and have the general formula
(I): Q.sup.+X.sup.- wherein Q.sup.+ is formula (a) or formula (b);
and X.sup.- is formula (c), formula (d) or formula (e); and
wherein: each of R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5,
R.sup.9, R.sup.10, R.sup.11, R.sup.12, and R.sup.13 is
independently a hydrocarbyl group; each of R.sup.6, R.sup.7, and
R.sup.8 is independently a hydrogen or hydrocarbyl group.
##STR1##
Inventors: |
Zhou; Yuehui; (Ontario,
CA) ; Robertson; Allan J.; (Ontario, CA) ;
Hillhouse; John H.; (Ontario, CA) ; Baumann;
Douglas; (Ontario, CA) |
Correspondence
Address: |
WIGGIN AND DANA LLP;ATTENTION: PATENT DOCKETING
ONE CENTURY TOWER, P.O. BOX 1832
NEW HAVEN
CT
06508-1832
US
|
Family ID: |
31722360 |
Appl. No.: |
10/521973 |
Filed: |
August 8, 2003 |
PCT Filed: |
August 8, 2003 |
PCT NO: |
PCT/CA03/01189 |
371 Date: |
July 18, 2006 |
Current U.S.
Class: |
548/335.1 ;
558/20; 558/208 |
Current CPC
Class: |
C07D 233/56 20130101;
C07C 305/06 20130101; C07F 9/4006 20130101; C07F 9/5407
20130101 |
Class at
Publication: |
548/335.1 ;
558/208; 558/020 |
International
Class: |
C07F 9/02 20060101
C07F009/02; C07D 233/02 20060101 C07D233/02; C07C 305/02 20060101
C07C305/02 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 16, 2002 |
CA |
2398682 |
Claims
1. A compound having the general formula (I): ##STR6## and wherein:
each of R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.9,
R.sup.10, R.sup.11, R.sup.12 and R.sup.13 is independently a
hydrocarbyl group; each of R.sup.6, R.sup.7 and R.sup.8 is
independently a hydrogen or a hydrocarbyl group; with the provisoes
that: (i) when Q.sup.+ is a phosphonium cation and X.sup.- is a
phosphate, or a phosphonate anion other than a phosphonate in which
R.sup.13 is perfluorohydrocarbyl, then R.sup.1, R.sup.2, R.sup.3,
and R.sup.4 each has three or more carbon atoms; (ii) when Q.sup.+
is a phosphonium cation and X.sup.- is a sulfate then the sum of
carbon atoms in R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is greater
than 4; (iii) when Q.sup.+ is an imidazolium cation, X.sup.- is not
a sulfate anion; and (iv) when Q.sup.+ is a phosphonium cation,
X.sup.- is methylsulfate, and one of R.sup.1, R.sup.2, R.sup.3, and
R.sup.4 is methyl, the others of R.sup.1, R.sup.2, R.sup.3, and
R.sup.4 cannot be 2-cyanoethyl.
2. A compound according to claim 1, wherein Q.sup.+ is a
tetralkylphosphonium and and X.sup.- is an alkylsulfate anion.
3. A compound according to claim 2, wherein R.sup.1, R.sup.2, and
R.sup.3 are hydrocarbyl groups with three or more carbon atoms.
4. A compound according to claim 2, wherein R.sup.1, R.sup.2, and
R.sup.3 are each n-butyl.
5. A compound according to any one of claims 2 to 4, wherein: (a)
R.sup.4 is methyl and R.sup.6 is methyl; or (b) R.sup.4 is ethyl
and R.sup.6 is ethyl; or (c) R.sup.4 is n-butyl and R.sup.6 is
n-butyl.
6. A compound according to claim 1, wherein the compound is
selected from the group consisting of
tri-(n-butyl)methylphosphonium methylsulfate;
tri-(n-butyl)ethylphosphonium ethylsulfate;
tetra-(n-butyl)phosphonium n-butylsulfate;
triethyl-(n-butyl)phosphonium n-butylsulfate; tetrabutylphosphonium
dibutylphosphate; tri-iso-butyl-butylphosphonium dibutylphosphate
N,N-dimethylimidazolium dimethylphosphate;
N-methyl-N-butylimidazolium dibutylphosphate; and
N-methyl-N-ethylimidazolium ethylethanephosphonate; and
tributylmethylphosphonium methyltrifluoromethanephosphonate.
7. A process for preparing a compound of formula (I): ##STR7## and
wherein: each of R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5,
R.sup.9, R.sup.10 R.sup.11, R.sup.12, and R.sup.13 is independently
a hydrocarbyl group; each of R.sup.6, R.sup.7, and R.sup.8, is a
hydrogen or hydrocarbyl group; with the provisoes that: (i) when
Q.sup.+ is a phosphonium cation and X.sup.- is a phosphate, or a
phosphonate anion other than a phosphonate in which R.sup.13 is
perfluorohydrocarbyl, then R.sup.1, R.sup.2, R.sup.3, and R.sup.4
each has three or more carbon atoms; (ii) when Q.sup.+ is a
phosphonium cation and X-- is a sulfate then the sum of carbon
atoms in R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is greater than 4;
(iii) when Q.sup.+ is an imidazolium cation, X.sup.- is not a
sulfate; and (iv) when Q.sup.+ is a phosphonium cation, X.sup.- is
methylsulfate, and one of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is
methyl, the others of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 cannot
be 2-cyanoethyl. the process comprising reacting a compound of
formula (II): ##STR8## wherein each of R.sup.1, R.sup.2, and
R.sup.3 is independently a hydrocarbyl group, or formula (III):
##STR9## wherein R.sup.5 is a hydrocarbyl group, and cation of
R.sup.6, R.sup.7 and R.sup.8 is independently a hydrogen or
hydrocarbyl group, with a compound defined by one of the following
formulae: ##STR10## wherein each of R.sup.4, R.sup.9, R.sup.10,
R.sup.11, R.sup.12 and R.sup.13 is a hydrocarbyl group.
8. The process of claim 7, wherein the reaction is carried out in
the absence of solvent.
9. The process of claim 7, wherein Q.sup.+ is a
tetralkylphosphonium and and X.sup.- is an alkylsulfate anion.
10. The process of claim 9, wherein R.sup.1, R.sup.2, and R.sup.3
are hydrocarbyl groups with three or more carbon atoms.
11. The process of claim 9, wherein R.sup.1, R.sup.2, and R.sup.3
are each n-butyl.
12. The process of any one of claims 7 to 11, wherein (a) R.sup.4
and R.sup.6 are both methyl; or (b) R.sup.4 and R.sup.6 are both
ethyl; or (c) R.sup.4 and R.sup.6 are both n-butyl.
13. The process of claim 7 or 8, wherein the compound of formula
(I) is selected from the group consisting of
tri-(n-butyl)methylphosphonium methylsulfate;
tri-(n-butyl)ethylphosphonium ethylsulfate;
tetra-(n-butyl)phosphonium n-butylsulfate;
triethyl-(n-butyl)phosphonium n-butylsulfate; tetrabutylphosphonium
dibutylphosphate; tri-iso-butyl-butylphosphonium dibutylphosphate
N,N-dimethylimidazolium dimethylphosphate;
N-methyl-N-butylimidazolium dibutylphosphate; and
N-methyl-N-ethylimidazolium ethylethanephosphonate; and
tributylmethylphosphonium methyltrifluoromethanephosphonate.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to novel phosphonium and
imidazolium salts, their methods of preparation and their use, for
example, as polar solvents.
BACKGROUND OF THE INVENTION
[0002] Low melting or liquid phosphonium and imidazolium salts have
found utility as polar solvents known as "ionic liquids". Ionic
liquids provide an attractive alternative to traditional organic
solvents for chemical reactions for many reasons. Ionics liquids
display low vapour pressure which, for industrial purposes, is a
very important feature. They are essentially non-volatile, a
property that eliminates many of the containment problems typically
encountered with traditional organic solvents. Since ionic liquids
are often composed of poorly coordinating ions, they have the
potential to provide a highly polar yet poorly coordinating
solvent. Moreover, many of these solvents are immiscible with
traditional organic solvents and therefore provide a non-aqueous
polar alternative for use in two-phase systems. Because of their
distinctive solvent characteristics, they can be used to bring
unusual combinations of reagents into the same phase. A recent
review of the properties and uses of ionic liquids is provided in
an article entitled "Room-Temperature Ionic Liquids. Solvents for
Synthesis and Catalysis," by Thomas Welton (Chem. Rev. 1999, 99,
2071-2083).
[0003] Ionic liquids provide solvents with a wide liquid range and
a high degree of thermal stability. However, there remains a need
for increasing the solvent options available to chemists by
developing novel ionic liquids with distinctive physical and
chemical properties.
[0004] Ionic liquids can be prepared by a two step process,
comprising the steps of (a) reacting a nitrogen-containing compound
(for example, imidazole) or a phosphorus-containing compound with
an alkylhalide to obtain a quaternary nitrogen or phosphorus halide
salt; and (b) exchanging the halide ion with a suitable anion (ion
exchange or metathesis) to obtain a low-melting quaternary nitrogen
or phosphorus salt. This process has several drawbacks. For
example, the end-product can be contaminated with residual halide
ion, which may interfere with the activity of halide-sensitive
catalysts. For instance, halide ions such as chloride ions
coordinate with group VII metals such as palladium and platinum. If
an ionic liquid is to be used in an environment where halide ions
are unacceptable, even at low levels, halide salts should not be
used in the starting materials or a further process must be used
which ensures removal of halide ions from the ionic liquid. Also,
the two-step process is inconvenient, as the ion-exchange step
produces salt or acid side-products that must be removed by washing
with water.
SUMMARY OF THE INVENTION
[0005] The current invention provides novel ionic compounds that
find utility as ionic liquids and methods of preparing these
compounds. The novel ionic compounds can have a broad range of
phosphonium or imidazolium cations and a broad range of sulfate,
phosphate or phosphonate anions
[0006] Thus, the current invention provides:
[0007] (1) a compound having the general formula (I): ##STR2## and
wherein:
[0008] each of R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5,
R.sup.9, R.sup.10, R.sup.11, R.sup.12 and R.sup.13 is independently
a hydrocarbyl group;
[0009] each of R.sup.6, R.sup.7, and R.sup.8 is independently a
hydrogen or hydrocarbyl group;
with the provisoes that:
[0010] (i) when Q.sup.+ is a phosphonium cation and X.sup.- is a
phosphate, or a phosphonate anion other than a phosphonate in which
R.sup.13 is perfluorohydrocarbyl, then R.sup.1, R.sup.2, R.sup.3,
and R.sup.4 each has three or more carbon atoms;
[0011] (ii) when Q.sup.+ is a phosphonium cation and X.sup.- is a
sulfate then the sum of carbon atoms in R.sup.1, R.sup.2, R.sup.3,
and R.sup.4 is greater than 4;
[0012] (iii) when Q.sup.+ is an imidazolium cation, X.sup.- is not
a sulfate anion; and
[0013] (iv) when Q.sup.+ is a phosphonium cation, X.sup.- is
methylsulfate, and one of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is
methyl, the other of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 cannot
all be 2-cyanoethyl.
[0014] In another aspect, the invention provides:
[0015] (1) a process for preparing a compound of formula (I), as
defined above, wherein:
[0016] (a) a compound of formula (II): ##STR3## wherein each of
R.sup.1, R.sup.2, and R.sup.3 is defined as above, or formula
(III): ##STR4## wherein each of R.sup.5, R.sup.6, R.sup.7 and
R.sup.8 is defined as above, is reacted with:
[0017] (b) a compound defined by one of the following formulae:
##STR5## wherein each of R.sup.4, R.sup.9, R.sup.10, R.sup.11,
R.sup.12 and R.sup.13 is defined as above.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0018] Suitable hydrocarbyl groups for R.sup.1, R.sup.2, R.sup.3,
R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8, R.sup.9, R.sup.10,
R.sup.11, R.sup.12 and R.sup.13 include: C.sub.1-C.sub.30 alkyl,
C.sub.3-C.sub.8 cycloalkyl, C.sub.2-C.sub.30 alkenyl,
C.sub.2-C.sub.30 alkynyl, C.sub.6-C.sub.11 aryl, or
C.sub.7-C.sub.30 aralkyl, although hydrocarbyl groups with not more
than 20 carbon atoms are preferred. It is noted that R.sup.13 can
also be a perfluoroalkyl group. It is possible for the groups
R.sup.1 to R.sup.12, and R.sup.13 when not perfluoroalkyl, to bear
substituents, or to include heteroatoms, provided that the
substituents or heteroatoms do not interfere with the preparation
of the compounds of the invention, and do not adversely affect the
desired properties of the compound. Acceptable substituents may
include alkoxy, alkylthio, halo, carboxy, amino, acetyl, and
hydroxyl groups, and heteroatoms that may be acceptable include
nitrogen, oxygen and sulphur. Substituents are likely to increase
the cost of the compounds of the invention and as the compounds are
often used as solvents, they are used in such volume that cost is a
significant factor. Hence, it is contemplated that, for the most
part, substituents will not be present, although compounds in which
R.sup.13 is perfluoroinated hydrocarbyl constitute a preferred
embodiment. If necessary, one of skill in the art can readily
determine whether substituents or heteratoms of the hydrocarbyl
groups interfere with preparation or desired properties of the
compounds by routine experimentation that does not involve the
exercise of any inventive faculty.
[0019] Preferred values for R.sup.1, R.sup.2, R.sup.3, R.sup.4,
R.sup.5, R.sup.6, R.sup.7, R.sup.8, R.sup.9, R.sup.10, R.sup.11,
R.sup.12 and R.sup.13 include alkyl groups of 1 to 20 carbon atoms,
for example, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl,
n-pentyl, cyclopentyl, isopentyl, n-hexyl, cyclohexyl,
(2,4,4'-trimethyl)pentyl, cyclooctyl, tetradecyl, etc. Alkyl groups
of 3 to 10 carbon atoms are especially preferred values for R.sup.1
to R.sup.13.
[0020] For compounds containing a phosphonium cation, it is desired
in some cases that R.sup.1 to R.sup.4 shall not be identical and
preferably, that at least one of R.sup.1 to R.sup.4 shall contain a
significantly higher number of carbon atoms than the others of
R.sup.1 to R.sup.4. Phosphonium cations in which R.sup.1 to R.sup.4
are not identical are referred to as "asymmetric".
[0021] In some cases, it is preferred that at least one of R.sup.1
to R.sup.13 contains a higher number of carbon atoms, for example
14 or more. For example, the presence of one or more long alkyl
chains may increase the ability of a phosphonium or imidazolium
salt to dissolve nonpolar organic compounds.
[0022] In general, it is preferred that the salt of the current
invention is a liquid below 100.degree. C., more preferably below
50.degree. C., and most preferably at or below room temperature.
Preferred compounds, therefore, are those in which the particular
groups R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5, R.sup.6,
R.sup.7, R.sup.8, R.sup.9, R.sup.10, R.sup.11, R.sup.12 and
R.sup.13, are selected to yield compounds that are liquid at room
temperature. In general, increasing the total number of carbon
atoms present in the hydrocarbyl groups R.sup.1 to R.sup.13 will
tend to increase the melting point, although this effect can be
counteracted somewhat by asymmetry and branching, and the tendency
of sterically bulky ions to coordinate poorly. For example, steric
bulk around the phosphorus atom or nitrogen atom of the cation or
the sulfur atom or phosphorus atom of the anion will tend to
decrease melting point of the salt and may be preferred. Therefore,
more preferred are compounds wherein each of R.sup.9, R.sup.10,
R.sup.11, R.sup.12, and R.sup.13 and one or more of R.sup.1,
R.sup.2, R.sup.3, and R.sup.4 or one or more of R.sup.4, R.sup.5,
R.sup.6, R.sup.7, and R.sup.8 has three or more carbon atoms. Also,
branching of the hydrocarbyl groups R.sup.1 to R.sup.13 tends to
decrease the melting point of the compound. Branching can occur at
the alpha or omega carbon or at any intermediate point. In cases
where the compound contains a phosphonium cation, the melting point
tends to decrease as the degree of asymmetry around the phosphorus
atom increases. For compounds containing an imidazolium cation, the
melting melt will tend to decrease as the degree of symmetry in the
imidazolium cation decreases.
[0023] For example, tetrabutylphosphonium dibutylphosphate is a
solid at room temperature, but tri(iso-butyl)(n-butyl)phosphonium
dibutylphosphate is a liquid at room temperature, despite the fact
that both compounds have 24 carbon atoms.
[0024] Notably, certain compounds of formula (I) may have melting
points below room temperature, below 0.degree. C. and even below
-20.degree. C., in which case they may be suitable for use as
solvents for reactions carried out at correspondingly low
temperatures. For example, tetrabutylphosphonium butylsulfate
remains a liquid at -20.degree. C.
[0025] Compounds according to formula (I) that are hydrophobic or
"water immiscible" are preferred for some purposes. The term "water
immiscible" is intended to describe compounds that form a two phase
system when mixed with water but does not exclude ionic liquids
that dissolve in water nor ionic liquids that will dissolve water,
provided that the two phase system forms. Compounds that have a
large total number of carbons, equal to or greater than 20 and in
particular greater than 25 or 26, or have at least one aryl group
are more hydrophobic. Water immiscibility is a desirable feature of
an ionic liquid not only because it renders the compound useful for
biphasic reactions with an aqueous phase, but also because it
facilitates purification and isolation of the ionic liquid when
prepared according to certain methods. There is no critical upper
limit on the total number of carbon atoms that may be present in a
compound of formula (I). However, it is unlikely that the total
will exceed 50.
[0026] Thus, the current invention contemplates compounds of
formula (I) where properties may be modified by varying the values
of the R groups present on either the anion or the cation.
Selection of particular values for R.sup.1 to R.sup.13 to achieve
particular melting points and degrees of water immiscibility is
within the competence of a person skilled in the art, although it
may require some routine experimentation.
[0027] Compounds according to formula (I) that have chirality
provide a chiral environment for chemical reactions and may be
especially preferred for certain purposes, such as a reaction
having an assymetric or chiral transition state that may be
stabilized by interaction with a suitable solvent. Examples of
chiral compounds of formula (I) include compounds containing a
phosphonium cation wherein R.sup.1 to R.sup.4 are all different or
one of R.sup.1 to R.sup.4 is an enantiomer, such as
2,4,4'-trimethylpentyl, which group has one chiral atom.
[0028] Examples of preferred compound according to formula (I)
include: [0029] tri-(n-butyl)methylphosphonium methylsulfate;
[0030] tri-(n-butyl)ethylphosphonium ethylsulfate; [0031]
tetra-(n-butyl)phosphonium n-butylsulfate; [0032]
triethyl-(n-butyl)phosphonium n-butylsulfate; [0033]
tetrabutylphosphonium dibutylphosphate; [0034]
tri-iso-butyl-butylphosphonium dibutylphosphate [0035]
N,N-dimethylimidazolium dimethylphosphate; [0036]
N-methyl-N-butylimidazolium dibutylphosphate; and [0037]
N-methyl-N-ethylimidazolium ethylethanephosphonate; and [0038]
tributylmethylphosphonium methyltrifluoromethanephosphonate.
[0039] In general, a phosphonium or imidazolium salt of formula (I)
can be prepared by reacting a compound of formula (II) or formula
(III), respectively, with one of the following: (1) a sulfate
diester of formula (IV); (2) a phosphate triester of formula (V);
or (3) a phosphonate diester of formula (VI).
[0040] In a preferred procedure for preparing compounds of formula
(I), a tertiary phosphine of formula (II) or an imidazole of
formula (III) is added directly to an ester (a sulfate diester,
phosphate triester, or phosphonate diester), with stirring. The
reaction is suitably carried out at an elevated temperature, for
example in the range of 140.degree. C. to 190.degree. C., under an
inert atmosphere.
[0041] The overall reaction is exothermic. Therefore, in order to
control the temperature of the reaction mixture, it may be
desirable to control the rate of addition in some cases and perhaps
also to apply external cooling during the addition step. Since
alkylphosphines may be pyrophoric, the addition of
trialkylphosphine should also be controlled in order to avoid
having a large amount of unreacted trialkylphosphine present in the
reaction mixture, especially when the reaction is being carried out
at elevated temperatures, for example over 100.degree. C.
[0042] In general, the phosphine or imidazole and ester are present
in the foregoing reaction in substantially stoichiometric amounts.
In some cases, however, yields may be improved by using a slight
molar excess of the phosphine or imidazole relative to the ester,
for example in the range of 1.01 to 1.4 equivalents and preferably
around 1.02 equivalents of the phosphine or imidazole.
[0043] Preferably, the reaction is carried out in the absence of
solvent, in order to avoid a further step of purifying product away
from solvent. However, the reaction may also be carried out in the
presence of a solvent. In some cases, the presence of a solvent may
be preferred as the solvent may enhance the rate at which the
reaction proceeds.
[0044] The temperature of the reaction is not critical, although
lower temperatures will result in longer reaction times. The
reaction proceeds readily at elevated temperature, say up to
220.degree. C., preferably in the range of 140-190.degree. C., and
is often complete in 8 hours at these temperatures. Certain
alkylating agents, such as dimethyl-sulfate, are very active
alkylating reagents and may be used for reactions carried out at
room temperature. The initial step of adding the ester compound to
the phosphine or imidazole, when required, may be conveniently
carried out at room temperature.
[0045] The pressure of the reaction is not critical, and the
reaction may be conveniently carried out at atmospheric pressure,
preferably under an inert atmosphere, such as nitrogen. It is
further preferable that the atmosphere be dry, in order to minimize
the water content of the product.
[0046] If desired, any unreacted starting materials and/or residual
water may be removed by, for example, drying under vacuum.
[0047] The foregoing process may be especially preferred if it is
desirable to avoid contamination of end-product with halide ions or
to avoid or minimize the amount of water contained in the
end-product. However, compounds of formula (I) may be prepared by
any suitable procedure.
[0048] The phosphonium and imidazolium salts of the current
invention may be used as polar solvents for chemical reactions such
as Michael additions, aryl coupling, Diels-Alder, alkylation,
biphasic catalysis, Heck reactions, hydrogenation, or for enzymatic
reactions, for example lipase reactions.
EXAMPLES
[0049] In the following examples, starting material phosphines are
made by Cytec Canada, Inc. and their purity determined by gas
chromatography (GC). N-methylimidazole and dibutylsulfate were
purchased form Lancaster. The remaining starting materials were
purchased from Aldrich and used as they were purchased. Structures
were confirmed by 1H-NMR, .sup.13C-NMR and .sup.31P-NMR.
Example 1
Preparation of tri-(n-butyl)methylphosphonium methylsulfate
[0050] To a flask containing 132 g (99% pure, 1.036 mole)
dimethylsulfate, at room temperature, tri(n-butyl)phosphine (218 g,
98% pure, 1.056 mole) was gradually added, over a period of three
hours, with stirring under nitrogen. The temperature in the flask
increased gradually to 100.degree. C. during the addition.
[0051] When the addition was complete, the reaction mixture as
heated to 150.degree. C. for 8 hours, then dried in a rotary
evaporator under 140.degree. C./5 mm Hg for 5 hours.
[0052] Tri-(n-butyl)methylphosphonium methylsulfate product was
obtained in 100% yield (348 g). NMR analysis was consistent with
tri-(n-butyl)methylphosphonium methylsulfate. The product was a
liquid at room temperature. .sup.1H-NMR(CDCl.sub.3, 300.13 MHz,
.delta.): 3.46 (s, 3H, --OCH.sub.3), 2.09 (m, 6H,
3.times.CH.sub.3CH.sub.2CH.sub.2--CH.sub.2--P.sup.+), 1.71 (d, 3H,
CH.sub.3P.sup.+), 1.32 (m, 12H,
3.times.CH.sub.3--CH.sub.2CH.sub.2--CH.sub.2P.sup.+), 0.76 (m, 9H,
3.times.CH.sub.3--CH.sub.2CH.sub.2CH.sub.2P.sup.+). .sup.31P-NMR
(CDCl.sub.3, 81.015 MHz, .delta.): 27.00 (P.sup.+).
Example 2
tri-(n-butyl)ethylphosphonium ethylsulfate
[0053] To a flask containing 100 g (98% pure, 0.636 mole)
diethylsulfate, at 60.degree. C., tri(n-butyl)phosphine (132 g, 98%
pure, 0.638 mole) was added gradually, over a period of two hours,
with stirring under nitrogen. The temperature in the flask
increased slowly to 120.degree. C. during the addition.
[0054] When the addition was complete, the reaction mixture was
heated to 150.degree. C. for 3 hours, then dried in a rotary
evaporator under 160.degree. C./5 mm Hg for 5 hours.
[0055] Tri-(n-butyl)ethylphosphonium ethylsulfate product was
obtained in 100% yield (230 g). Analysis by NMR was consistent with
tri-(n-butyl)ethylphosphonium ethylsulfate. The product was a
liquid at room temperature. .sup.1H-NMR(CDCl.sub.3, 300.13 MHz,
.delta.): 4.05 (q, 2H, --O--CH.sub.2--CH.sub.3), 2.34 (m, 6H,
3.times.CH.sub.3CH.sub.2CH.sub.2--CH.sub.2--P.sup.+), 2.34 (m, 2H,
CH.sub.3--CH.sub.2--P.sup.+), 1.27 (m, 3H,
CH.sub.3--CH.sub.2P.sup.+), 1.27 (m, 3H, --OCH.sub.2--CH.sub.3),
0.97 (m, 9H, 3.times.CH.sub.3--CH.sub.2CH.sub.2CH.sub.2P.sup.+).
.sup.31P-NMR (CDCl.sub.3, 81.015 MHz, .delta.): 35.05
(s,P.sup.+).
Example 3
tetra-(n-butyl)phosphonium butylsulfate
[0056] To a flask containing: 50 g (95% pure, 0.226 mole)
di-(n-butyl)sulfate, at 80.degree. C., tri(n-butyl)phosphine (48 g,
98% pure, 0.233 mole) was gradually added, over a period of one
hour, with stirring under nitrogen. The temperature in the flask
increased gradually to 120.degree. C. during the addition.
[0057] When the addition was complete, the reaction mixture was
heated to 190.degree. C. for 8 hours, then dried in a rotary
evaporator under 160.degree. C./5 mm Hg for 5 hours.
[0058] Tetra-(n-butyl)phosphonium n-butylsulfate product was
obtained in 96% yield (90 g). Analysis by NMR was consistent with
tetra-(n-butyl)phosphonium n-butylsulfate but indicated that the
product contained some impurity. The product was a liquid at room
temperature. .sup.1H-NMR(CDCl.sub.3, 300.13 MHz, .delta.): 3.77 (t,
2H, --OCH.sub.2--CH.sub.2CH.sub.2CH.sub.3), 2.09 (m, 8H,
4.times.CH.sub.3CH.sub.2CH.sub.2--CH.sub.2--P.sup.+), 1.41 (qu, 2H,
--OCH.sub.2--CH.sub.2--CH.sub.2CH.sub.3), 1.33 (m, 16H,
4.times.CH.sub.3--CH.sub.2CH.sub.2--CH.sub.2P.sup.+), 1.19 (qu, 2H,
--OCH.sub.2CH.sub.2--CH.sub.2--CH.sub.3), 0.76 (m, 12H,
4.times.CH.sub.3--CH.sub.2CH.sub.2CH.sub.2P.sup.+), 0.76 (m, 3H,
--OCH.sub.2CH.sub.2CH.sub.2--CH.sub.3). .sup.31P-NMR (CDCl.sub.3,
81.015 MHz, .delta.): 33.49.
Example 4
Synthesis of tri-ethyl(n-butyl)phosphonium butylsulfate
[0059] Triethylphosphine (7.2 g, 99%, 0.06 mol) was added dropwise
to a 125 mL flask containing 12.6 (99%, 0.06 mol) di-n-butylsulfate
at 80.degree. C. under nitrogen and with stirring over a period of
75 minutes. The liquid was stirred at 140.degree. C. for an
additional 3.5 hours. The liquid was cooled, moved to a rotary
evaporator and dried at 125.degree. C./5 mm Hg for 6 hours. The
product (16.73 g, yield 85%) was a wax-like solid at room
temperature (m.p. from DSC measurement: 40.0.degree. C.).
.sup.1H-NMR(CDCl.sub.3, 300.13 MHz, .delta.): 3.98 (t, 2H,
CH.sub.3CH.sub.2CH.sub.2--CH.sub.2--O--), 2.34 (m, 8H,
3.times.CH.sub.3--CH.sub.2P.sup.+ and
CH.sub.3CH.sub.2CH.sub.2--CH.sub.2P.sup.+), 1.54 (m, 8H,
CH.sub.3--CH.sub.2CH.sub.2--CH.sub.2O-- and
CH.sub.3--CH.sub.2CH.sub.2--CH.sub.2P.sup.+), 1.25 (m,
3.times.CH.sub.3--CH.sub.2P.sup.+), 0.91 (m, 6H,
CH.sub.3CH.sub.2CH.sub.2--CH.sub.2O-- and
CH.sub.3CH.sub.2CH.sub.2--CH.sub.2P.sup.+). .sup.31P-NMR
(CDCl.sub.31 81.015 MHz, .delta.): 38.88 (s, P.sup.+).
Example 5
Synthesis of tetrabutylphosphonium dibutylphosphate
[0060] Tri-n-butylphosphine (215 g, 94%, 1.0 mole) was added
dropwise over a period of 4 hours to a flask containing 272 g (98%,
1.0 mole) of tributylphosphate at 170.degree. C. When the addition
was complete, the reaction mixture was heated to 200.degree. C. and
stirred at this temperature for 24 hours. The viscous liquid was
dried in a rotary evaporator at 160.degree. C./5 mm Hg for 5 hours.
The product (363 g, yield 77.5%) was pure according to NMR. At room
temperature the product was a white, wax-like solid (m.p. from DSC
measurement: 28.0.degree. C.). .sup.1H-NMR(CDCl.sub.3, 300.13 MHz,
.delta.): 3.84 (q, 4H,
2.times.CH.sub.3CH.sub.2CH.sub.2--CH.sub.2--O--), 2.38 (m, 8H,
4.times.CH.sub.3CH.sub.2CH.sub.2--CH.sub.2P.sup.+), 1.53 (m, 16H,
4.times.CH.sub.3--CH.sub.2CH.sub.2--CH.sub.2P.sup.+), 1.40 (m, 8H,
2.times.CH.sub.3--CH.sub.2CH.sub.2--CH.sub.2O--), 0.97 (m, 12H,
4.times.CH.sub.3--CH.sub.2CH.sub.2CH.sub.2P.sup.+), 0.90 (m, 6H,
2.times.CH.sub.3--CH.sub.2CH.sub.2CH.sub.2O--). .sup.31P-NMR
(CDCl.sub.3, 81.015 MHz, .delta.): 33.72 (P.sup.+), 0.94 [m,
(RO).sub.2--P(.dbd.O)--O.sup.-].
Example 6
Synthesis of tri-iso-butyl-butylphosphonium dibutylphosphate
[0061] Tri-iso-butylphosphine (206.5 g, 98%, 1.0 mole) was added
dropwise over a period of 2 hours to a flask containing 271.8 g
(98%, 1.0 mole) of tributylphosphate at 200.degree. C. under
nitrogen and stirring. When the addition was complete, the mixture
was stirred at the same temperature for an additional 15 hours. The
mixture was cooled down and moved to a rotary evaporator and dried
under 160.degree. C./5 mm Hg for 5 hours. The product (320.7 g,
yield 68.5%) was pure judged from NMR and liquid at room
temperature. .sup.1H-NMR(CDCl.sub.3, 300.13 MHz, .delta.): 3.76 (q,
4H, 2.times.CH.sub.3CH.sub.2CH.sub.2--CH.sub.2O--), 2.19 (q, 6H,
3.times.CH.sub.3 (CH.sub.3)CH--CH.sub.2P.sup.+), 1.96 (m, 3H,
3.times.CH.sub.3 (CH.sub.3)CH--CH.sub.2P.sup.+), 1.96 (m, 2H,
CH.sub.3CH.sub.2CH.sub.2--CH.sub.2P.sup.+), 1.44 (m, 8H,
CH.sub.3--CH.sub.2CH.sub.2--CH.sub.2O--), 1.24 (m, 4H,
CH.sub.3--CH.sub.2CH.sub.2--CH.sub.2P.sup.+), 1.01 (d, 18H,
3.times.CH.sub.3CH(CH.sub.3)--CH.sub.2P.sup.+), 0.84 (t, 3H,
CH.sub.3--CH.sub.2CH.sub.2CH.sub.2P.sup.+), 0.77 (t, 6H,
2.times.CH.sub.3--CH.sub.2CH.sub.2CH.sub.2O--). .sup.31P-NMR
(CDCl.sub.3, 81.015 MHz, .delta.): 32.60 (P.sup.+), -0.61 [d,
(RO).sub.2--P(.dbd.O)--O.sup.-].
Example 7
Synthesis of N,N-dimethylimidazolium dimethylphosphate
[0062] Trimethylphosphate (127.6 g, 0.883 mole) was added dropwise
over a period of 1 hour to a 300 ml flask containing 72.2 g (99%,
0.87 mole) N-methylimidazole at room temperature. The temperature
of the reaction mixture was slowly increased to 140.degree. C. As
the reaction mixture approached 140.degree. C., there was an
acceleration in the rate at which the temperature increased. The
reaction mixture was stirred at the same temperature for an
additional 3 hours. The mixture was cooled and moved to a rotary
evaporator and dried at 150.degree. C./5 mm Hg for 4 hours. The
product (194 g, yield 100%) was pure, judged from NMR and liquid at
room temperature. .sup.1H-NMR(CDCl.sub.3, 300.13 MHz, .delta.):
10.40 (s, 1H, --N--CH.dbd.N--), 7.43 (s, 2H, --N--CH.dbd.CH--N--),
3.91 (s, 6H, N--CH.sub.3), 3.46 (d, 6H, --OCH.sub.3). .sup.31P-NMR
(CDCl.sub.3, 81.015 MHz, .delta.): 3.01 [s,
(RO).sub.2--P(.dbd.O)--O.sup.-].
Example 8
Synthesis of N-methyl-N-butylimidazolium dibutylphosphate
[0063] Tributylphosphate (137.2 g, 0.505 mole) was added dropwise,
slowly, to a 300 ml flask containing 41.5 g (99%, 0.5 mole)
N-methylimidazole at 170.degree. C. under nitrogen and stirring.
The liquid was stirred at the same temperature for an additional 5
hours. The liquid was cooled and moved to a rotary evaporator and
dried at 150.degree. C./5 mm Hg for 4 hours. The product (171.3 g,
yield 98%) was pure, as judged from NMR, and was liquid at room
temperature. .sup.1H-NMR(CDCl.sub.3, 300.13 MHz, .delta.): 10.37
(s, 1H, --N--CH.dbd.N--), 7.50 (s, 1H, --N--CH.dbd.CH--N--),
7.29)s, 1H, --N--CH.dbd.CH--N--), 4.09 (t, 2H,
--N--CH.sub.2--CH.sub.2CH.sub.2CH.sub.3), 3.87 (s, 3H,
--N--CH.sub.3), 3.67 (m, 4H,
--O--CH.sub.2--CH.sub.2CH.sub.2CH.sub.3), 1.67 (qu, 2H,
--NCH.sub.2--CH.sub.2--CH.sub.2CH.sub.3), 1.40 (m, 4H,
2.times.--OCH.sub.2--CH.sub.2--CH.sub.2CH.sub.3), 1.16 (m, 4H,
--OCH.sub.2CH.sub.2--CH.sub.2--CH.sub.3), 1.16 (m, 2H,
--NCH.sub.2CH.sub.2--CH.sub.2CH.sub.3), 0.70 (m, 6H,
2.times.--OCH.sub.2CH.sub.2CH.sub.2--CH.sub.3), 0.70 (m, 3H,
--NCH.sub.2CH.sub.2CH.sub.2--CH.sub.3). .sup.31P-NMR (CDCl.sub.3,
81.015 MHz, .delta.): 0.95 [s, (RO).sub.2--P(.dbd.O)--O.sup.-].
Example 9
Synthesis of N-methyl-N-ethylimidazolium ethylethanephosphonate
[0064] Diethylethanephosphonate (68.2 g, 99%, 0.406 mole) was
dripped into a 300 ml flask containing 33.3 g (99%, 0.402 mole)
N-methylimidazole at 160.degree. C. under nitrogen and stirring
over a period of 80 minutes. The liquid was stirred at the same
temperature for an additional 10 hours. The liquid was cooled,
moved to a rotary evaporator and dried at 140.degree. C./5 mmHg for
2.5 hours. The product (92.4 g, yield 92%) was a liquid at room
temperature. .sup.1H-NMR(CDCl.sub.3, 300.13 MHz, .delta.): 10.99
(s, 1H, --N--CH.dbd.N--), 7.73 (s, 1H, --N--CH.dbd.CH--N--), 7.65
(s, 1H, --N--CH.dbd.CH--N--), 4.39 (q, 2H,
--N--CH.sub.2--CH.sub.3), 4.09 (s, 3H, --NCH.sub.3), 3.92 (m, 2H,
--O--CH.sub.2--CH.sub.3), 1.56 (m, 3H, --OCH.sub.2--CH.sub.3), 1.56
(m, 2H, --(O.dbd.)P--CH.sub.2--CH.sub.3), 1.19 (m, 3H,
--(O.dbd.)PCH.sub.2--CH.sub.3), 1.19 (m, 3H,
--NCH.sub.2--CH.sub.3). .sup.31P-NMR (CDCl.sub.3, 81.015 MHz,
.delta.): 25.57 [s, RO--(R)P(.dbd.O)--O.sup.-].
Example 10
tetraalkylphosphonium alkyl alkanephosphonate
[0065] Tetraalkylphosphonium alkyl alkanephosphonate compounds can
be made by reacting a trialkylphosphine with a dialkyl
alkanephosphonate according to the process described in Example 1
except that dialkyl alkane phosphonate is used in place of
dimethylsulfate.
[0066] Dialkyl alkanephosphonates which are used as starting
materials can be made according to the Michaelis-Arbuzov reaction:
(RO).sub.3P+R'CH.sub.2X.fwdarw.(RO).sub.2P(.dbd.O)CH.sub.2R'+RX
[0067] Typical Michaelis-Arbuzov reactions and conditions for
carrying out the reactions are described in a review article by A.
K. Bhattacharya, G. Thyagarajan, Chemical Review, 1981, volume 81,
page 415 the contents of which are herein incorporated by
reference. Michaelis-Arbuzov reactions specifically for making
dialkyl fluorinated alkanephosphonates, as exemplified by the
synthesis of diethyl trifluoromethanephosphonate, are described in:
T. Mahmood, J. M. Shreeve, Synthesis Communications, 1987, 17(1),
71-75, (the contents of which are herein incorporated by reference)
and in D. J. Burton, R. M. Flynn, Synthesis, 1979, 615. In
addition, V. I. Shibaev, A. V. Garabadzhiu, A. A. Rodin, Zh.
Obshch. Khim. 1983, 53(8), 1743-1745 (the contents of which are
herein incorporated by reference) describes a method for
synthesizing di(isobutyl)trifluoromethanephosphonate.
[0068] By way of illustration, in a typical reaction, one
equivalence of the alkylhalide R'CH.sub.2X is added slowly into a
flask containing 1.3-2 equivalence of trialkylphosphite (RO).sub.3P
through an addition funnel under stirring. The excess of the
trialkylphosphite can serve as solvent for the reaction. The
reaction may be carried out over a range of temperatures, for
example in the range of room temperature to 150.degree. C.
Preferably, the reaction is carried out at a temperature below the
boiling points of the starting materials. The boiling point of
trimethylphosphite is 112.degree. C., triethylphosphite is
155.degree. C. If an elevated reaction temperature is preferred,
the trialkylphosphite in the flask can be preheated to that
temperature. After all material has been added the flask, the
reaction mixture can be refluxed for a suitable period of time,
typically several hours. Any remaining unreacted trialkylphosphite
and the byproduct alkylhalide R'X of the reaction can be removed by
evaporating the mixture under vacuum.
[0069] The foregoing reaction may be used to make partially and
completely fluorinated alkane phosphonates for use in making salts
of formula (I). For example, when a compound represented by the
general formulae C.sub.nF.sub.2n+1I is used as the alkyl halide in
the foregoing reaction, the resulting Michaelis-Arbuzov phosphonate
is a dialkyl perfluoroalkanephosphonate. When reacted with a
trialkylphosphine, the resulting phosphonium salt is a
tetraalkylphosphonium alkyl perfluoroalkanephosphonate, which
compounds may be especially preferred for some applications, such
as two-phase reactions where one phase is aqueous and the ionic
liquid phase is necessarily hydrophobic.
* * * * *